Using a method called 'attitude flying,' they can control their aircraft by determining the relationship between the aircraft's nose, or front end, and the horizon.

Pilots use the horizon to keep aircraft level while in the air. Importance of the Horizon The concept of the horizon is important to different types of work, including aviation, navigation, and art. From orbit, the true horizon is spherical, following the shape of the Earth. The true horizon is the imaginary plane that passes through the center of the Earth, perpendicular to its radius. Astronomical horizons are great circles that surround the observer. The astronomical horizon is the imaginary horizontal plane always at a 90-degree angle from the observer's zenith (the point directly above the observer).

They are measurements of the position of the Earth relative to the rest of the sky. Celestial Horizons Celestial horizons are used by astronomers. If you're standing on the beach looking out at the sea, the part of the sea that 'touches' the horizon is called the offing. The ocean and the sky provide a clean, flat line where the Earth seems to meet the sky. One of the best places to see the sea-level horizon is a beach. The sea-level horizon is the geographic horizon at sea level. Mountains, trees, and other elevated features are not considered part of the geographic horizon. The geographic horizon is the apparent boundary between the Earth and sky. The local horizon may include trees, buildings, and mountains. Earth-Sky Horizons The local horizon, also called the geometrical horizon, is the visible boundary between the Earth and sky. The astronomical horizon and true horizon are celestial horizons. The local horizon, geographic horizon, and sea-level horizon are all Earth-sky horizons. Both Earth-sky and celestial horizons have different sub-types of horizons. There two main types of horizons-Earth-sky horizons and celestial horizons.

The horizon is the line that separates the Earth from the sky.

Celestial horizon definition